Patterning of polymeric layers is a crucial step in the manufacturing of microelectronic devices. For example, integrated electronic circuits are manufactured using a plurality of photolithography steps performed in sequence to form features of electronic components on chip. Each of these lithography steps involves the exposure of a polymeric photosensitive layer (photoresist) to a ultra-violet (UV) light through a chromium photomask and the chemical development of the photoresist layer. The process allows transferring a pattern from the mask to the photoresist.
This process allows creating high definition patterns in a photoresist layer which can be used, for example, to selectively deposit a metal line or implant dopant atoms. The process also allows to precisely aligning the pattern with features already present on the integrated circuit.
Photolithography steps have also been used to fabricate high efficiency laboratory solar cells, such as the PERL solar cell at the University of New South Wales, and the A300 solar cell at the University of Stanford. Despite the record results of these solar cells, photolithography is not a viable solution for the production of commercial solar cells.
The cost of photomasks and the photoresist material does not comply with the low cost requirement of the solar cell manufacturing industry. In addition, the time required for aligning the photomasks to the devices, exposing and developing the photoresist does not comply with the high throughput requirement of modern solar cell manufacturing lines.
A patterning step may be used at different stages of the solar cell manufacturing process. For example, a patterning step may be required to selective deposit a metal to form conductive fingers on a surface of a solar cell. A patterning step may be also used in many other applications, for example, the deposition of protecting coatings on glass substrates, the formation of conductive patterns on electronic boards, etc.
These applications generally do not require the resolution and alignment precision typical of the photolithography techniques used in the microelectronic industry.
There is a need for a method which can be used to pattern a polymeric layer which allows for a higher throughput and has a lower cost than conventional photolithography.